The deal raises questions over Mr Blair’s role as a Middle East peace envoy and whether he has used that position to befriend wealthy rulers in Abu Dhabi, the capital of the United Arab Emirates (UAE), who are now funding his private consultancy work in Colombia, among other countries.

The disclosure will add to pressure on Mr Blair to quit as envoy. According to one well-placed source, he is expected to announce his resignation from the role in the coming weeks.

Chris Doyle, director of the Council for Arab-British Understanding, a cross-party body campaigning for greater links with Arab countries, said: “This raises serious questions of a conflict of interest over Mr Blair’s roles as businessman and Middle East envoy.

“The UAE is supposed to be a leading donor government on the issue of Gaza and the West Bank, so what does Tony Blair put first, his role as Quartet envoy or his role as a businessman when dealing with them? What is the nature of all these contracts? There is still a lack of transparency about it.”

The contract has also prompted concern in Colombia over why UAE was funding Mr Blair’s advisory role in the country, with one senior prosecutor writing to the president demanding an inquiry.

The year-long contract was signed on Oct 22, 2013, between Windrush Ventures No 3 LP, a limited partnership set up by Mr Blair to channel fees for work done by TBA on behalf of foreign governments, and Colombia’s department of national planning.

TBA signed a further contract with Colombia in 2014, offering advice on the management of unspecified, major projects.

Windrush Ventures No 3 LP does not need to publish accounts and can legitimately keep its income hidden from public scrutiny.

A page from Mr. Blair's 2013 contract with Colombia

The 2013 contract, which runs to 34 pages, gave Mr Blair and his team the power to conduct “a stocktake” of Colombia’s numerous mining deals, worth £2 billion a year in royalties paid by outside companies for mining concessions.

The contract states no fees are being paid to TBA by the Colombian government. But the Colombian government has admitted that “the United Arab Emirates through the Office of Tony Blair [Windrush Ventures No 3 LP] domiciled in the UK” had signed an agreement “to support the implementation” of the new rules on how money from mining deals is distributed in Colombia.

Mr Blair is estimated to have earned between £50 million and £100 million since quitting as prime minister, largely through his consultancy businesses. Among those consultancy jobs, Mr Blair is a paid adviser to Mubadala, Abu Dhabi’s sovereign wealth fund which bought a gold mine in Colombia two months ago.

UAE is also understood to pay TBA’s fees for advising governments in Serbia and Vietnam. It is not clear how much those contracts are worth but one source has claimed Abu Dhabi could be paying £30 million in fees.

The contract with Colombia also discloses:

• How Mr Blair used his status as former prime minister to secure the deal, boasting that “improved delivery was one of the great achievements of the Blair administration”. • TBA boasts it is better than any local consultancy because it works with the “founders of deliverology”, a New Labour model for government reform. • How Mr Blair insists on strict secrecy in his business dealings with no fewer than 10 clauses dealing with confidentiality. • Documents relating to Mr Blair which are not directly connected to the contract must be handed over and destroyed. • How one specific clause entitles his wife Cherie Blair to accompany him on any visit to Colombia.

The contract gives Mr Blair and his team an influential role in Colombia in overseeing changes to the way the money from mining deals is redistributed in the country.

TBA promises under the terms of the contract to conduct a stocktake of Colombia’s mining deals and to develop “systems and processes for monitoring, control and evaluation” of those deals to ensure that money paid to Colombia by mining companies for the right to extract minerals is not misappropriated.

The contract offers a fascinating insight into Mr Blair’s commercial dealings and further opens him up to accusations he has traded on his influence and contacts gained in Downing Street. Mr Blair is close friends with Colombia’s president Juan Manuel Santos, a multi-millionaire media tycoon, with whom Mr Blair co-wrote a political book in 1999.

Colombia’s prosecutor for public affairs, Fanny María González Velasco, has written to the president, demanding an explanation as to Mr Blair’s role over concerns already aired in public that “Blair obtains all the necessary information and passes it to the Arabs so that all will be easier for them when they come to do business in Colombia”.

The prosecutor has questioned the suitability of Mr Blair as an adviser to the government when he is paid by the UAE.

The contract includes 10 subsections dealing with confidentiality, which include stipulations that documentation should be headlined “private and strictly confidential” and that copies of documents should only be made “when it is absolutely necessary”.

Each document and disk containing information considered confidential must be listed on a register, stating where each documents is held and who holds them. At the end of the period of the contract, all material not directly related to the project itself must be handed over to Mr Blair’s team or destroyed.

Under the terms of the contract, Mr Blair’s team must stay in “first class” hotels and specifies what types of printers and internet connections must be made available to his team on the ground.

Mr Blair agrees to make two trips a year to Colombia and the contract allows him to bring with him whom he likes. The contract specifically states these people could include his wife Cherie.

Mrs Blair has no involvement in TBA although her law firm Omnia Strategy has picked up lucrative contracts — as previously disclosed by The Telegraph — in other countries where Mr Blair is an official government adviser, including Kazakhstan and Albania. The contracts are worth about £750,000.

Mr Blair’s business proposal, contained in an annex to the contract, boasts: “Mr Blair, with his extensive on-the-job experience and politician instincts, will personally lead this project.

“Typically his contribution will go beyond the narrow focus of the specific project, and our growing understanding of the situation on the ground will allow Mr Blair to serve as an adviser to the government in several other areas, be it in domestic matters or questions of international politics.”

The Emirates Palace

TBA claims the deal can save the Colombian taxpayer $1.5 billion (£1bn) by putting into place an effective system of management of “extraction royalties” owed to the Colombian state through mining deals. In the proposal, TBA uses diagrams and flow charts to demonstrate how it can help the government. TBA says it will use “deliverology”, a pseudoscientific term coined by New Labour. The contract states: “All our team members will have expertise in … deliverology or mining induced growth strategies.”

The contract was agreed after Colombia introduced a law in 2011 under which fees and royalties from the mining industry were sent back to central government. Before, about 80 per cent of such mining “royalties” were kept by the local region. It is not clear if Mr Blair had any involvement in the framing of the new legislation. He was already working with the Colombian government as long ago as 2009 as an adviser to Mr Santos.

Mr Blair’s spokesman confirmed that the TBA team in Colombia was being paid for by UAE but denied any conflict of interest from the deal. The spokesman said: “TBA has been working with the Colombian Government since 2013. There is absolutely nothing improper in this project being funded by UAE.